Ammonium Nitrate: The Hidden Danger and Storage Risks

Understanding the Nature of Ammonium Nitrate

Ammonium nitrate (AN), often seen as a simple fertilizer, is not as harmless as it might seem. It is classified as a tertiary high explosive, meaning it is classified as highly explosive, but very difficult to detonate. Properly designed explosive devices are required to successfully trigger its detonation. To detonate a substance like AN for industrial purposes, one would typically use a leading cap, such as lead azide, to facilitate the ignition of a secondary explosive like PETN (pentaerythritol tetranitrate), TNT (trinitrotoluene), or dynamite.

A common industrial use for ammonium nitrate is in ANFO (Ammonium Nitrate Fertilizer Oil). This mixture is created by adding fuel oil to ammonium nitrate, which leverages the extra oxygen available in AN. The resulting mixture is utilized in large-scale quarry operations and has historically been used in some infamous terrorist attacks, such as the Oklahoma City bombing and the earlier attack on the World Trade Center before 9/11.

The Beirut Explosion and Ammonium Nitrate Hazards

The Beirut explosion of August 4, 2020, highlighted the severe dangers associated with improperly stored ammonium nitrate. Lebanon had 2,750 tons of AN in storage. While other materials like sodium cyanide and calcium carbide were also present, the primary cause of the explosion was the ammonium nitrate. The explosion's significant blast radius and devastating impact on the nearby residential area underscored the catastrophic potential of ammonium nitrate when not stored and managed correctly.

The perilous nature of ammonium nitrate storage was vividly demonstrated in the Halifax explosion of 1917. A ship carrying 2,900 tons of nitroglycerin and 100 tons of AN for ammunition factory production triggered a massive explosion when it collided with a French ship. The force of the explosion destroyed Halifax's port, killed over 2,000 people, and injured an additional 9,000. Similarly, a fertiliser plant in Galveston, Texas, with an estimated 3,000 tons of AN, exploded shortly after World War II, causing widespread destruction.

Why Incorrect Storage Can Lead to Explosive Mixtures

The risks associated with ammonium nitrate storage often originate from improper management and lack of awareness regarding its explosive properties. Storing ammonium nitrate alongside flammable materials, like fireworks or other reactive chemicals, significantly increases the likelihood of a disastrous event. For example, in the Tianjin disaster of 2015, the warehouse storing ammonium nitrate had other flammable materials, including calcium carbide. When the carbide got wet and produced acetylene, which caught fire and ignited a shipping container of ammonium nitrate, it quickly turned into a massive detonation.

Further evidence of the risks comes from the Beirut explosion. In this case, ammonium nitrate was found alongside fireworks in a storage warehouse. When the fireworks caught fire, the ammonium nitrate ignited in a deflagration, which then turned into a powerful detonation. The catastrophic results, including the loss of life and significant property damage, could have been minimized if the proper safety measures had been taken.

Key Takeaways on Ammonium Nitrate Storage

To prevent such catastrophic events, proper storage and management of ammonium nitrate are essential. Here are some critical points to consider:

Understanding its explosive nature: Recognize ammonium nitrate as a highly explosive substance even if it is not typically considered an explosive. Segregation: Store it away from flammable materials, combustibles, and other reactive chemicals. Training: Ensure all personnel involved in storage and handling are trained in proper safety procedures. Risk assessment: Conduct regular risk assessments to identify and mitigate potential hazards.

In conclusion, the Beirut explosion serves as a stark reminder of the significant risks posed by improperly stored ammonium nitrate. Proper storage, coupled with thorough hazard management and training, can significantly reduce the risk of catastrophic events. Awareness and proactive measures are the key to ensuring safe handling and storage, not only for ammonium nitrate but for other high-risk chemicals as well.